Improving the Frequency Characteristics of RF Standard Magnetic-Field Generator Employing Loop Antenna

In the HF and VHF region, the standard magnetic-field generator having a loop antenna has been generally used for the calibration of a radio receiver or a field-strength meter. Presented are new standard magnetic field generators which are able to produce a constant magnetic field over a wide band frequency range by means of measuring the loop current through a compensation transmission line and a compensation thermination resistor. A magnetic-field generator in which a thermistor was used as both a compensation resistor and a current sensor was constructed and examined over the frequency range 10 to 50 MHz. The measured values were agreed with theoretical values within ±0.1 dB.